Rotor pivot



Patented Oct. 31, 1944 UNITED STATE s PATENT OFFICE no'ron P vo'rSamuelBousky, Shaker Heights, Ohio, assignor,

by mesne assignments, to Jack & Heintz, Incl, Cleveland, Ohio, acorporation of Ohio Application August 2, 1943, Serial No. 497,04

7 Claims. (Cl. 308178) This invention relates in general to high speedrotors, such as gyro wheels, and more particularly to improvements inpivots therefor.

In the proper balancing of gyro rotors it has been found that shiftsofodynamic balance occur due to temperature variations. It has beencommon practice to use a gyro rotor whose hub is made of aluminum,magnesium or other light weight material having a high coefiicient ofexpansion and with a pivot made of steel or other rugged material havinga relatively low coefiicient of expansion. It has been found that as thehub contracts upon decrease in temperature, I

or expands upon increase in temperature, due to difference in expansioncoefficients, a shear stress is built up at the surface boundary-betweenthe pivot and hub. Since this shear stress is op- "posed only by thefrictional forces between the two surfaces, slippage occurs between themwhen the stress becomes sufficiently great. Since the a frictionalforces are not uniform throughout the surface boundary, when theslippage occurs, a radial as well as axial change of the pivotpositionoccurs, thus altering thedynamic balance and these shifts occur inconsequence of an increase as well as a decrease in temperature.v

Accordingly the invention has for its primary object to provide aself-contained unitary pivot that will be sufficiently rugged for use insuch a high speed rotor as a gyro rotor and yet be prethermallystabilized so as to automatically compensate for temperature changesover a wide range. i I

With this in mind it is proposed to build the pivot primarily of suchmetal as steel including its bearing end surfaces and to incorporateinto t e intermediate portion of the hollow barrel of he pivot a hollowbarrel, or insert. of metal having a relatively high coefficient ofexpansion Figure 1 is a view, partly in end elevation and partly incross section of a gyro rotor, the axis pivot and the bearings therefor;and

Figure2 is anenlarged view in side elevation of the pivot, showing theinterior thereof in dotted lines.

Referring more particularly to the drawing, the rotor I itself is ofconventional design and construction, the main ,body portion, includingthe hub 2 and rim 3 being made ofv somesuch light weight metal asmagnesium or aluminum having a high coefiicient of expansion andseparate outer rim strips Aandti of heavy metal applied on either sideof the rotor buckets 6. The rotor is carried by a pivot whose endbearing portions I and 8 are rotatably supported by bearingassembliesincluding balls ,9 and I0 and such as aluminum, or the like.and thesame coefficient of expansion as the hub of the rotor itself andapproximately the same length as the width of the rotor hub so that asthe insert and the hub expand and contract uniformly laterally theinsert will act to accordingly shiftthe steel pivot ends and avoidslippage between the same and the rotor hub.

With the foregoing and other objects in view, the invention resides inthe combination of parts and in the details of construction hereinafterset forth in the following specification and a pended claims, certainembodiments thereof being illustrated in the accompanying drawing, inwhich:

races II and I2. I

In conventional construction the pivot is made of one piece of steel, asare the bearings therefor, and the rotor and its hub of magnesium. Dueto the difference in coefficients of expansion of these two metals, asharp increase or decrease in temperature brings about a shear stress atthe surface boundary between the pivot and hub slightly less diameterthan the steel portions 1 and -8 so as to not engage the hub 2. The twowing portions lie interiorly of the steel portions 1 and 8. and has itshollow bore-l6 align with those, I! and 18, of the steel portions 1 and8.

It is to be understood that the choice of 'magnesium or aluminum for therotor hub, steel for the pivot ends and magnesium or aluminum and thesame material as the hub for the pivot insert are merely preferentialand not binding as a limitation insofar as the'present invention isconcerned. Steelfor the pivot ends and bearings is preferred for itsdurability and low coefficient of expansion. Magnesium or aluminum ischosen for the rotor hub because of its lightness of weight. Theimportant factor, insofar as the pivot insert is concerned is to have itfabricated of the same material as the rotor hub. It may be preferableto form the rotor Upon temperature increase the hub 2 will exi I pandlaterally and likewise contract laterally upon temperature decrease. Dueto the difference in the coefificients of expansion of the magnesium, oraluminum, of the rotor hub the tendency ordinarily would be to obtainunequal expansion and contraction of the two resulting in shear stressbetween the boundary surfaces and slippag'es and shifts of dynamicbalances. However, inasmuch as the coefficient of expansion of theinsert is the same as that of the rotor hub, the expansion orcontraction of the insert results in the lateral shifting of the steelpivot ends so as to prevent any shear stresses between the boundarysurfaces of the steel pivot ends and the rotor hub.

It will be seen from the foregoing that due to the presence of themagnesium or aluminum insert intermediate thegtwo steel pivot end bearinportions, the radial clearance between the .insert and the magnesiumcraluminum rotor hub and the axial clearance between the wings of theinsert and the steel bearing portions, tema perature compensation over aWide temperature ran e from extreme heat to extreme cold has. beennrovided so as to avoid slippages, bindings and shifts of dynamicbalances.

I claim:

1.. In comb nation with a rotor a p vot up n which said rotor is mountedand bearings for carryin said pivot. the hub portion of said rotor beingformed of a material of a relatively high coeflicient of expansion andthe end bearing;

port ons of said pivot being formed of a material of relatively lowcoefficient of expansion, said pivot having a web portion intermediateof said end portions formed of a material having a relatively highcoefiicient of expansion.

2. In combination with a rotor, a pivot upon which said rotor is mountedand bearings for carrying said pivot, the hub portion of said rotorbeing formed of a material of a relatively high coefficient of expansionand the end bearing portions of said pivot being formed of a material ofrelatively low coefiicient of expansion, said pivot having a web portionintermediate of said end portions formed of a material having arelatively high coefficient of expansion substan-,,

tially equal to that of said rotor hub.

3. In combination with a rotor, a pivot upon which said rotor is mountedand bearings for carrying said pivot, the hub portion of said rotorbeing formed of a material of a relatively.

high coeflicient of expansion and the end bearing portions of said pivotbeing formed of a material of relatively low coeificient of expansion,said pivot having a web portion intermediate of said end portions formedof a material.

having a relatively high coefficlent of expansion and of substantiallythe same length as the width of said rotor hub.

4. In combination with a rotor, a pivot upon which said rotor is mountedand bearings for carrying said pivot, the hub portion of said rotorbeing formed of a material of a relatively high coefiicient of expansionand the end bearing portions of said pivot being formed of a material ofrelatively low coeflicient of expansion, said pivot having a web portionintermediate of said end portions formed of a material having arelatively high coeflicient of expansion substantially equal to that ofsaid rotor hub and of substantially the same length as the width of saidrotor hub.

5. In combination with a rotor, a pivot upon which said rotor is mountedand bearings for carrying said pivot, the hub portion of said rotorbeing formed of a material of a relatively high coeificient of expansionand the end bearing portions of said pivot being formed of a material ofrelatively low coeflicient of expansion, said pivot having a web portionintermediate of said end portions formed of a material having arelatively'high coetficient of expansion substantially equal to that ofsaid rotor hub and of substantially the same length as the width of saidrotor hub, said intermediate web portion being of less diameter thanthe'remaining end portions of said pivot. v

6. In combination with a rotor, a pivot upon which said rotor is mountedand bearings for carrying said pivot, the hub portion of said rotorbeing formed of a material of a relatively highcoe'fiicient of expansionand the end bearing portions of said pivot being formed of a material ofrelatively low coefiilcient of expansion, said pivot having a webportion intermediate oi said end portions formed'of a material having arelatively high coeificient of expansion substantially equal to that ofsaid rotor hub and of substantially the same length as the width of saidrotor hub, said intermediate Web portion including a central portion ofless diameter than the remaining pivot end portions and separating thesame, the remaining portion of said intermediate web being overlapped bysaid pivot end portions. v

7. In combination with a rotor, a pivot upon which said rotor is mountedand bearings for carrying said pivot, the hub portion of said rotorbeing formed of a material of a relatively high coefiic'ient ofexpansion and the end bearing portions of said pivot being formed of amaterial of relatively low coefficient of expansion, said pivot having aweb portion intermediate of said endportions formed of a material havinga rela tively high coefiicient of expansion substantially equal to thatof said rotor hub, said web portion and said hub being separately formedand having abutting shoulders whereby said web portion, having arelatively high coefficient of expansion is adaptedupon temperaturevariations to laterally shift said pivot end bearing portions to avoidshear stresses between the boundary surfaces of the latter and the rotorhub.

SAMUEL BOUSKY.

